Well I dont know about the 4's, but my 88 YJ with a 6 has one on it and mine went out a while back and I just told them the year and model and the new one was the same and I figured the 4s did to, maybe someone took it off of yours somewhere down the road in the past and put the one thats there on it.

Know way to tell i suppose but its definitely not a clutched fan, with the engine off if i spin it the whole engine turns, I'm thinking a clutch fan will help it warm up faster in the winter and maybe free up some engine power when not in use.

LOL you bought a PO jury rig then. All the YJ's had a clutch fan. With the 2.5L that thing is taking a bunch of your horse power. Get rid of it totally and go to the Taurus fan. You will get more horse power and better cooling for under $100. It's well worth it and not much more then the clutch will cost you. I can tell the difference big time with my 89 2.5L.

Know way to tell i suppose but its definitely not a clutched fan, with the engine off if i spin it the whole engine turns, I'm thinking a clutch fan will help it warm up faster in the winter and maybe free up some engine power when not in use.

(2.5L engine power) < lol

One way for a fan clutch to go out is that they will lock up. Sounds like your fan clutch locked up.

The electric fan is better by a long shot for mudding and water. The mechanical and electric fan trying to push through the mud and water destroys them. Most people put a kill switch to toggle off the electric fan which is something you just can't do with the mechanical fan. The fan being seized like that is making your engine work way harder then it should eating up your fuel and is trying to push mud and water when you are sloshing the heap in a crossing. You really shouldn't leave it seized up.